An uninterruptible power source device is a power source device that supplies electric power from a previously charged secondary battery to a loading device for continuing the operation of the loading device, in a state in which electric power is not supplied from an external power source to the loading device due to electric power interruption or the like. The secondary battery of the uninterruptible power source device is generally charged with the electric power of the external power source, at normal times. As an example of the secondary battery that is used in the uninterruptible power source device, an alkaline secondary battery such as a nickel-hydrogen secondary battery is publicly known, for example.
The alkaline secondary battery, from its nature, needs to be charged at a voltage that is higher than the rated voltage. However, generally, in the uninterruptible power source device, the rated voltage of the alkaline secondary battery is the same as the voltage of the external power source. Therefore, at that voltage, the alkaline secondary battery cannot be charged to a full-charge state, with the electric power of the external power source.
For this reason, there is publicly known an uninterruptible power source device including an auxiliary power source (DC/DC converter) that raises the voltage of the external power source. More specifically, at the time of the charge of the alkaline secondary battery, the voltage of the external power source is raised by the auxiliary power source, and the alkaline secondary battery is charged at the raised voltage. Thereby, even in the case of an alkaline secondary battery with a rated voltage that is the same as the voltage of the external power source, the alkaline secondary battery can be charged to the full-charge state, at a voltage that is higher than the rated voltage. Further, although not an uninterruptible power source device, as an example of the technology that uses the auxiliary power source, there is publicly known a motor control device to increase, by the auxiliary power source, the amount of the electric power that can be supplied to an electric motor, when the electric power demand of the electric motor increases temporarily (see Patent Document 1, for example).